xloadimage -- arbitrary command execution when handling compressed files

Tavis Ormandy discovered that xli and xloadimage attempt to decompress images by piping them through gunzip or similar decompression tools. Unfortunately, the unsanitized file name is included as part of the command. This is dangerous, as in some situations, such as mailcap processing, an attacker may control the input file name. As a result, an attacker may be able to cause arbitrary command execution.